SecurityPkg: Replace VariableLock with VariablePolicy Since VariableLock compromises security in the SMM environment, it is deprecated. Used VariablePolicy instead for stronger and more flexible UEFI variable protection. Ref: [acd66e4] Cc: Sachin Ganesh <sachinganesh@ami.com> Signed-off-by: Sathya Ravichandran <sathyar@ami.com>